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It comes as no real surprise that the bullpen has developed into a weakness for the Minnesota Twins. That much was easy enough to foresee in spring training. After some surprising early success gave way, we've reached a point where Paul Molitor has basically one reliever he can trust.

That one reliever happens to be quite possibly the best in the game at what he does, but Glen Perkins needs some help if the Twins want to hang on as contenders in the AL Central.

Before the season started, it appeared that the organization might have plenty of options for late-inning reinforcements around this point in the summer. But those options have dried up in shocking fashion over the first half, helping illustrate the volatility of relief prospects in general.

No player exemplifies this better than Nick Burdi. He was perhaps the most dominant college closer in the country with Louisville before being drafted 46th overall last year, and had all the looks of an MLB-ready arm while mowing through the low minors in July and August. Between two levels of A-ball, he struck out 38 hitters in 20 innings. No one stood a chance.

Burdi opened this season at Double-A, and got on track after a rough first month, rattling off shutdown appearances for five weeks from May into June. Then the wheels fell off, leading to a demotion to back to Single-A. Suddenly, the idea of Burdi helping this year seems far-fetched.

He's not the only fast-rising arm to stall out at Chattanooga this year. Jake Reed, another 2014 pick who blew through the low levels after being drafted out of college, has been knocked around by Double-A hitters for a 5.40 ERA and 1.48 WHIP. Fellow fireballer Zack Jones landed on the disabled list last week following a trainwreck outing in which he walked four and allowed four runs.

These are the big power arms that were viewed as potential wild cards coming into the season. They're not going to help, and it doesn't look like the Twins are going find a difference-maker at Triple-A either. Michael Tonkin has been ineffective in a few stints with Minnesota, Lester Oliveros is injured, and Alex Meyer... yikes.

A.J. Achter has put up dazzling numbers, and got a bit of big-league experience last September, but as was the case with Anthony Slama, there clearly is skepticism about how his stuff will play in the majors. Despite already being on the 40-man roster and posting otherworldly numbers at Triple-A (he has a 0.80 WHIP, and that's after giving up four runs in his last outing), he has been bypassed for promotions by Ryan Pressly, Meyer, and Tonkin twice.

Almost everywhere you look, things are going awry for the numerous prospects that Minnesota hoped might provide a midseason bullpen jolt. The few that are healthy and performing are evidently not trusted. So if the Twins want an impactful upgrade, they will need to look externally to the trade market.

Check in Friday at Twins Daily, where we'll explore the options there, as well as the merits of making a move.